Apparatus for processing a plurality of articles or materials



March 9, 1965 w. F. GRIFFIN APPARATUS FOR PROCESSING A PLURALITY 0F ARTICLES OR MATERIALS m w M W W 1 7/ fi/ r /4/// m 4 W! m 0 Q 5 M M United States Patent 3,172,244 APPARATUS FOR PRQCESSING A PLURALITY 0F ARTICLES QR MATERIALS William F. Griflin, Summit, N.J., assignor to Radio Corporation of America, a corporation of Delaware Continuation of application Ser. No. 58,068, Sept. 23,

1960. This application Dec. 7, 1961, Ser. No. 159,816

21 Claims. (Cl. 53-86) This invention relates to apparatus for heat treating, evacuating and seal-ing evacuated articles, and particularly, with an improved means for batch heat treating, evacuating and sealing electron tubes.

This application is a continuation of my copending application, Serial Number 58,068, filed September 23, 1960, and now abandoned.

While this invention will :be described in connection with the processing of electron tubes, it is not so limited in its utility but has useful fuetions wherever vacuum and heat treating of articles is desirable.

One type of apparatus employed on a relatively large scale for processing electron tubes to provide an evacuated and sealed envelope is known as a sealex machine. This type of machine includes two turrets, on one of which a stem wafer is sealed to a bulb of an electron tube, and on the other of which the envelope formed by the stern and bulb is evacuated through an exhaust tubulation fornung part of the envelope, and the tubulation then sealed off to completely and permanently seal the envelope.

However, certain other newly developed tube types having no exhaust tubulation in .the envelopes thereof and requiring sealing of envelope parts after evacuation cannot be processed by conventional sealex machines.

For processing such other tube types and similar work pieces, use has been made of what is commonly known as a bell jar system. This system, which is a batch rather than a continuous process, includes a large demountable bell jar connected to a means of evacuation and containing a means of heating the work pieces therewithin.

A disadvantage in the use of hell jar systems, however, is that the length of time required to process each batch of work pieces is often excessively long. This is especially true in the processing of certain types of electron tubes, for example, wherein, for reasons to be described hereinafter, the sealed tubes must be cooled before they may be exposed to the atmosphere.

Means for introducing coolants into the bell jar systems to hasten cooling are known, but these means are undesirable for cost reasons. The initial expense of providing apparatus having the necessary valve and conduit means for introducing the coolant into the system is high, and the coolants used are a further expense. Self-cooling systems are thus to be preferred, but the times required for cooling presently known simple and inexpensive selfcooling systems are excessively long.

Moreover, the time required to initially heat the exhaust apparatus and the work pieces therein is objectionally long.

It is an object of this invention to provide an improved and inexpensive apparatus for batch processing work pieces to be heat treated, evacuated and sealed off.

More particularly, it is an object of this invention to provide an improved self-cooling batch processing apparatus wherein the time required to heat and subsequently cool the work pieces is reduced.

For achieving these and other objects, an exhausting and heating apparatus is provided which comprises a hermetically scalable envelope enclosing a tubular chamber. The tubular chamber is adapted to receive the work pieces to be processed, the chamber walls being made from electrically resistive material. Upon passage of current through the chamber walls, the chamber and the work pieces therein are heated. Means are also provided for evacuating the envelope, the tubular chamber and the work pieces therein.

According to one feature of this invention, the mass of the exhausting and heating apparatus is reduced by providing a tubular chamber having very thin Walls. As well known, the smaller the mass of an object, the more rapidly may it be heated to a given temperature, the less heat energy will it store at that temperature, and the more rapidly may it be cooled.

According to another feature of this invention, means for supporting and making electrical connections to ends of the tubular chamber comprise headers and a compacted, interwoven mesh of metallic strips, or metallic wool, disposed between the headers and the chamber. The metallic wool provides a low resistance, low

walls. heat loss electrical connector to the tubular chamber while also providing a firm chamber support which is pliable and yielding for allowing stress-free thermal expansion of the tubular chamber. discussed in greater detail hereinafter, use of metallic wool in accordance with this invention makes it possible to employ tubular heating chambers having exceptionally thin walls for greatly reducing the heating and cooling time of the work piece processing apparatus.

A further feature of this invention is the provision of a large, uniformly heatable work piece processing space for uniformly processing all the work pieces contained therein. This is achieved by fabricating the supported end lengths of the tubular chamber from a material having a high thermal resistivity and the central length of the chamber from a material having a low thermal resistivity. The low thermal resistivity central length permits an even distribution of the heat energy over the length thereof, while the high thermal resistivity end lengths prevent excessive heat losses by conduction through the end lengths to the supporting headers. In this manner, as will be more fully discussed hereinafter, the central portion of the tubular chamber, and hence the space included therein, is uniformly heated.

Further features and advantages of the invention will become apparent as the present description of an embodiment thereof proceeds.

In the drawing to which reference is now made for a consideration of one embodiment of the invention, by way of example:

FIG. 1 is an enlarged view in elevation, partly broken away, of envelope work pieces that may be processed by an apparatus according to the invention; and

FIG. 2 :is a longitudinal section of an apparatus embodying the invention.

Referring to FIG. 1, the work pieces to be produced by the apparatus of this invention may comprise a metal bulb 10 made of steel, for example, and an electron tube mount including a stem wafer 12 made of a ceramic, such as forsterite, having lead wires 14 extending therethrough and supporting electrodes therein, as shown in FIG. 1. A ring 16 of any well known soldering material is deposited adjacent to the periphery of the wafer 12 and the inside of the bulb 19, which is closed by positioning the wafer 12 therein. A suitable soldering material may consist of an alloy which is approximately 12% germanium and 88% copper, having a melting point of about 985 (3., which is commercially available. The periphery of the wafer 12 may have a metallic coating thereon, made of molybdenum, for example.

Processing of the described work pieces by apparatus made according to this invention involves degassing the metal components of the electron tube by heating, activating a cathode, also by heating, and sealing the periphery of the wafer 12 to the inner wall of the bulb 10.

Moreover, as will be To prevent the wafer 12 from falling out of the bulb in the position shown in FIGS. 1 and 2, a number of dimples 1 3 are provided in the bulb 10 for achieving a friction fit of. the wafer to the bulb.

Sufficient communication between the space defined by the bulb and wafer and the exterior is provided, nevertheless, so that when the parts referred to are placed in an ambient of reduced gas pressure, the gas pressure within the envelope formed by the bulb and wafer is reduced correspondingly. Furthermore, in the position of the electron tubes, as shown in FIGS. 1 and 2, a heating of the solder ring 16 to its melting point temperature will cause the melted solder to flow downwardly between the periphery of the wafer 12 and the inner wall of the bulb 10, to provide a hermetic seal therebetween when the solder is cooled to hardness.

For accomplishingthe foregoing heat treatment and vacuum' processing of the electron tube work pieces described, an apparatus according to this invention is provided which comprises an evacuating and heating chamber 20 including a cylindrical chamber envelope 21 closed at each end'by headers 23 and 24. Evacuation of chamber 20 -is provided by suitable evacuating means (not shown), which communicates with chamber 20 through a duct 26 opening into an aperture 27 extending through header 24.

Duct 26 terminates in flange 2-8; flange 28, envelope 21, and headers 23 and 24 being squeezed together in vacuumtight relationship against gaskets 30 and 32 by four tie rods 31.

Included within chamber 20 and adapted to receive the electron tube work pieces therein is an open ended tubulation 34, end lengths 36 thereof being received and supported within headers 23 and 24, as will be described more fully hereinafter. Loading of the electron tubes into tubulation 34 takes place through aperture 37 extending through header 23, and evacuation of tubulation 34 and the tubes therein takes place through aperture 27 extending through header 24.

For'properly locating electron tube Work pieces within tubulation 34, a charging rack 38 is provided which comprises an elongated basket-like structure adapted to receive and support the electron tubes with the bulbs 1 and the wafers 12 thereof'in proper loosely assembled relation.

Charging rack 38 is so designed that when a loaded rack 38 is inserted into tubulation 34, as shown in FIG. 2, none of the tubes supported on rack 38 is positioned within the end lengths 36 of tubulation 34. The purpose of this, as will be seen, is to insure that all the tubes in each processing batch are heat treated in the same manner.

After a batch of electron tubes is inserted within tubulation 34, chamber 20 is closed by cover plate 49. Upon evacuation, atmospheric pressure forces cover plate 49 against gasket 33 in header 23. to provide .a simple and excellent hermetic seal of the chamber from the atmosphere.

The electron tubes are processed within tubulation 34, as mentioned, and to provide heating thereof, the walls of tubulation 34 are made of electrically resistive material. Headers 23 and 24 are made of conducting material, and a complete electrical path is provided from an electrical energy source (not shown), through electrical connectors (indicated by the letter A in FIG. 2) to headers 23 and 24, through the metallic Wool packing 45, and through the walls of tubulation 34. The purpose of the metallic wool will be discussed more fully hereinafter. Upon passage of current through the electrically resistive tubulation walls, the walls are heated and the work pieces are heated-by radiation therefrom.

Suitable insulation spacers are provided for preventing shorting of headers 23 and 24 through the tie rods 31. Gaskets 30 are made from insulating material, such as silicon,-which prevents shorting of the headers by the chamber envelope 21, which may be of aluminum. Also, insulating beads 39 on charging rack 38 space the charg- 23 and 24 are provided with passageways 55 and 56 through which cooling water is continuously circulated. Also, the inside of chamber envelope 21 is silver surfaced to reflect back the radiant heat from the incandescent tubulation 20. Shields 47 and 48 having shiny inner surfaces are provided surrounding tubulation 34 to further reducethe heat energy radiated to envelope 21. As shown in FIG. 2, shield 47 is suspended header 23 and does not extend all the way to header 24 in order to prevent electrical shorting therebetween, shield 48 closing the otherwise exposed length of tubulation 34.

In the processing of electron tubes of the type described, it is known that the temperature of the tubes during processing must be carefully controlled to achieve the proper degree of cathode activation, outgassing of the tube metal parts, and proper sealing of the tube envelope. Thus, in the simultaneous batch processing of a number of tubes, it is essential that the work piece processing space be uniformly heated throughout the entire extent thereof.

For achieving such a uniformly heatable processingspace, in accordance with this invention, the electron tube receiving tubulation 34 is fabricated from materials having certain desired thermal and electrical conductivities. The centrally disposed length 49 of tubulation 34 is made from a material having relatively high thermal and electrieal conductivities, such as molybdenum. The end lengths 36 of tubulation 34, which are received within headers 23 and 24, are made from a material (such as Nichrome) having relatively low thermal and electrical conductivities in comparison to those of the central length 49 material.

Upon passage of current through the tubulation walls, heating of both the central and end lengths of the tubula tion occurs. 'Because the tubulation end lengths 36 are received withinthe relatively cool headers 23 and 24, heat energy will flow by conduction from these end lengths through the metallic wool 45 to the headers. Because of the relatively low thermal conductivity of the end lengths 36, however, the heat loss to the headers is small, and portions of the end lengths 36 spaced slightly outside headers 23 and 24 will reach a high temperature. Since the tubulation portions bounding the central length 49 are thus at a high temperature, the temperature gradient therebetween is small and there is little heat loss by conduction from the central length 49 to the end lengths 36. Moreover, because of the high thermal conductivity of the central length 49, the heat energy produced along this length \w'll flow readily in response to any temperature gradients therein whereby the temperature differential or gradient along thecentral length 49 is kept small.

The end lengths 36 are made of a higher electrical resistivity material than the central length 49 to dissipate electrical energy therein at a greater rate than in the central length. This is necessary to raise the temperature of portions of the end lengths 36 to a temperature close to that of the central length 49 in spite of the conductive heat losses from the end lengths 36 to the headers 23 and 24.

After'processing and sealing of the electron tube work pieces, it is desirable to cool the work pieces as rapidly as possible to shorten the work piece processing cycle and permit processing of the largest number of work piece batches in a given time. In the sealing of the electron tubes of the type described, it is not possible to expose the heated and processed tubes to the cooler atmosphere until the tubes have cooled to a temperature below 250 C., the tubes having been heated to a temperature of around 1060 C. for sealing. The reason for this is that exposure of the ceramic base wafer 12 to the near usual room temperature atmosphere While the wafer is above this 250 temperature may cause breakage of the wafer due to thermal shock. Moreover, until the sealing solder cools to a temperature below 250 C., exposure of the solder to the atmosphere causes oxidization thereof which results in poor sealing of the wafers 12 to the bulb 10, as known.

As known, the smaller the mass of an object, the less heat will it store at any temperature, and hence the more rapidly may it be cooled. In accordance with this invention, the mass of tubulation 34 and hence the time required to cool chamber 20 and the sealed tubes therein by radiation is greatly reduced by making the wall of tubulation 34 very thin. A further advantage of the thin walled tubulation is that it also reduces the time required to heat the apparatus and the electron tubes therein because of the small amount of energy required to heat the tubulation to the desired temperature.

A feature of this invention, as mentioned, is the use of metallic wool whereby it is possible to provide tubulation work piece receiving chambers having extremely thin walls. The reasons for this will now be discussed.

Some of the requirements for'rnaterials which may be used for tubulation 34 are as follows: the materials mustbe refractory and able to Withstand repeated exposures to temperatures in the range of 1200 C.; they must be relatively gas free to prevent contamination of the electron tubes; and they must be relatively strong to permit fabrication of very thin walled tubulations therefrom. It has been found that refractory metals, such as molyb denum and tungsten and alloys such as Nichr-ome which is composed of approximately 80% nickel and 20% chromium, and Kovar which is composed of approximately 54% iron, 29% nickel and 17% cobalt, are most satisfactory for this purpose.

A disadvantage to the use of such materials, however, is that their low electrical resistivities require that the heating electrical energy must be supplied as low voltage, high current power. This, in turn, requires that the electrical connections to tubulation 34 be of extremely low resistance to prevent excessive localized heating and possible melting of the thin wall tubulation. Moreover, because of the high currents involved, the connection to the tubulation must have a large area to prevent high current density flow into a small area of the tubulation which would also cause excessive heating and melting thereof.

Further, because of the fragile nature of the thin walled tubulation, the mechanical support thereof must be yieldable to permit stress-free thermal expansion of the tubulation upon heating.

The requirements for the electrical connector and support means for the thin walled tubulation 34 are thus that the connector be firmly and tightly secured to the tubulation while permitting free thermal expansion thereof, and the connection to the tubulation must cover a large area. Because of the fragile nature of the thin wall tubulation 20, known simple and inexpensive connecting and supporting means, such as ring clamps and the like, are not suitable because use of such means in tight, large area engagement to the tubulation would cause possible distortion, buckling, and collapse of the tubulation walls.

In accordance with this invention, all these requirements are met simply, inexpensively, and adequately by the use of the metallic wool packing in the arrangement as mentioned above.

The metallic wool 45 consists of an interwoven mesh of metallic fibers or strands, and may be commercially available steel wool. Copper or molybdenum wool are to be preferred, however, because of the greater electrical conductivities of copper and molybdenum as compared to steel. The strands of the wool may be, for example, .001-.002 inch thick, and .003.008 inch wide.

As shown in FIG. 2, the end lengths 36 of tubulation 34 extend part way into apertures 37 and 27 within headers 23 and 24, respectively, the smallest diameters of apertures 37 and 27 being slightly larger than the diameter of tubulation 34. Within apertures 37 and 27, a space is provided bounded by the walls of the apertures, the tubulation end length 36, and a washer 50. Packed within this space, and disposed between headers 23 and 24 and the end lengths 36 of tubulation 34 is the metallic wool 45. The walls of the apertures are threaded, and a plug 51 is threaded therein which bears on washer 50. By screwing plug 51 inwardly of apertures 37 and 27, the metallic wool is tightly compacted to support and make tight electrical contact to a large portion of the periphery of tubulation 34.

Although an excellent low resistance connection is thereby made between the tubulation and the headers, the metallic wool nevertheless retains sufl'icient pliancy and resiliency to permit stress-free thermal expansion of the tubulation.

In one embodiment of this invention, the central length 49 of tubulation 34 is about 6%. inches long and made from .003 inch molybdenum. The end lengths 36 are about 1% inches in length and are made from .005 inch Nichrorne.

The temperature variation along the central length 4-9. of the tubulation was found to be less than 5 C at a temperature thereof of 1100 C. The time to cool the work pieces from 1060 C. to 250 C. is less than eight minutes. In a prior art apparatus having the same dimensions but a tubulation wall thickness of .070 inch, the cooling time is forty-five minutes. The time to heat the work pieces from room temperature to processing temperature of about 860 C. is less than thirty seconds. The sealing gaskets 30 and 32 are made from silicon, and because of the low temperature at which they are maintained, the low vapor pressure produced therefrom permits exhaust of chamber 20 to a pressure of 10- mm. of mercury.

What is claimed is:

1. Apparatus for evacuating and sealing articles of manufacture comprising a chamber for receiving said articles, means for hermetically sealing said chamber, means for evacuating said chamber, headers for receiving portions of said chamber, and metallic wool disposed between said portions and said headers for yieldingly supporting said chamber within said headers and for making electrical contact therebetween. 1

2. Apparatus for evacuating and sealing articles of manufacture comprising an elongated tubular chamber for receiving said articles, means for hermetically sealing said chamber, means for evacuating said chamber, conductive headers for receiving end portions of said tubular chamber, and compacted metallic wool disposed between said end portion and said headers for yieldingly supporting said tubular chamber within said headers and for making low resistance electrical contact therebetween.

3. Apparatus for evacuating and sealing articles of manufacture comprising a chamber for receiving said articles, said chamber having a centrally disposed length made of an electrically resistive material and end lengths made of an electrically resistive material, the material of said end lengths having a higher thermal resistivity than the material of said centrally disposed length, conductive headers for receiving end portions of said chamber, metallic wool disposed between the end portions of said chamber and said headers, electrical energy contacting means connected to said headers for providing current through the walls of said chamber for heat processing said articles, and evacuating means communicating with said chamber for evacuating said articles.

4. Apparatus for evacuating and sealing articles of manufacture comprising a chamber for receiving said articles, said chamber having a centrally disposed length made of an electrically resistive material having a low thermal resistivity and end lengths made :of an electrically resistive material having a thermal resistivity higher than that of said central length material, conductive headers for'receiving end portions of said chamber, metallic wool disposed between the end portions of said chamber and said headers, electrical energy contacting means connected to said headers for providing current through the walls of said chamber for heat processing said articles, and evacuating means communicating with said chamber for evacuating said articles.

5. Apparatus for evacuating and sealing articles of manufacture comprising a tubular member providing a chamber for receiving said articles, said tubular member having a centrally disposed length made of an electrically resistive material having a low thermal resistivity and end lengths made of an electrically resistive material having a thermal resistivity higher than that of said central length material, conductive headers for receiving end portions of said tubular member, compacted metallic wool disposed between the end portions of said tubular member and said headers, electrical energycontacting means connected to said headers for providing current through said tubular member for heat processing said articles, and evacuating means communicating with said tubular member for evacuating said articles. a

6. Apparatus for evacuating and sealing articles of manufacture comprising an inner tubular member providing an elongated chamber for receiving said articles, said inner tubular member including a centrally disposed length made of an electrically resistive material having a low thermal resistivity, and end lengths made of an electrically resistive material having a thermal resistivity higher than that of said central length material, an outer tubular member surrounding and hermetically enclosing said inner tubular member, the inner surface of said outer tubular member being shiny and highly reflective of radiant heat energy, conductive headers for receiving end portions of said inner and outer tubular members, compacted metallic wool disposed between the end portions of said inner tubular member and said headers for yieldingly supporting said inner tubular member within said headers, electrical energy contacting means connected to said headers for providing current through said headers and said inner tubular members, and evacuating means communicating with said outer and said inner tubular members for evacuating said articles. H

7. Apparatus for evacuating and sealing articles of manufacture comprising an inner tubular member providing an elongated chamber for receiving said articles, said inner tubular member including a centrally disposed length having a Wall thickness of .003 inch made of an electrically resistive material having a low thermal resistivity, and end lengths having a Wall thickness of .005 inch made of an electrically resistive material having a thermal resistivity higher than that of said central length material, an outer tubular member surrounding and hermetically enclosing said inner tubular member, the inner surface of said outer tubular member being shiny and highly reflective of radiant heat energy, conductive headers for receiving end portions of said inner and outer tubular members, compacted metallic wool disposed between the end portions of said inner tubular member and said headers for yieldingly supporting said inner tubular member within said headers and for making low resistance electrical contact between said headers and a large portion :of the periphery of said inner tubular member, electrical energy contacting means connected to said headers for providing current through said headers and said inner tubular members, a tubular heat shield disposed between said inner tubular member and said outer tubular member, and evacuating means communicating with said outer and said inner tubular members for evacuating said articles.

8. Apparatus as in claim 6 wherein said centrally disposed length is made from molybdenum, and said end lengths are made from Nichrome. V i

9. Apparatus for evacuating and sealing articles of manufacture comprising an elongated chamber foi re ceiving said articles, means for hermetically sealing said chamber, means for evacuating said chamber, headers for receiving portions of said chamber, and metallic wool disposed between one of said portions and one of said headers for yieldingly supporting said one portion within said one header and for making electrical contact therebetween.

10. Apparatus for evacuating and sealing articles of manufacture comprising an elongated tubular chamber for receiving said articles, means for hermetically sealing said chamber, means for evacuating said chamber, conductive headers for receiving end portions of said tubular chamber, and compacted metallic wool disposed between one of said end portions and one of said headers for yieldingly supporting said one end portion withinsaid one header and for making low resistance electrical contact therebetween.

11. Apparatus for evacuating and sealing articles of manufacture comprising an elongated chamber for re ceiving said articles, said chamber having a centrally disposed length made of an electrically resistive material and end lengths made of an electrically resistive material, conductive headers for receiving end portions of said charnher, metallic wool disposed between one of said end portions of said chamber and one of said headers, electrical energy contacting means connected to said headers for providing current through the walls of said chamber for heat processing said articles, means for hermetically sealing said chamber, and evacuating means communicating with said chamber forevacuating said articles.

12. Apparatus for evacuating and sealing articles of manufacture comprising an elongated chamber for receiving said articles, said chamber having a centrally disposed length made of an electrically resistive material having a low thermal resistivity and end lengths made of an electrically resistive material having a thermal resistivity higher than that of said central length material, conductive headers for receiving end portions of said chamber, metallic wool disposed between one of said end portions of said chamber and one of said headers, electrical energy contacting means connected to said headers for providing current through the walls of'said chamber for heat processing said articles, and evacuating means communicating with said chamber for evacuating said articles.

13. Apparatus for evacuating and sealing articles of manufacture comprising an elongated tubular member providing a chamber for receiving said articles, said tubular member having a centrally disposed length made of an electrically resistive material having a low thermal resistivity and end lengths made of an electrically resistive material having a thermal resistivity higher than that of said central length material, conductive headers for receiving end portions of said tubular member, cornpacted metallic wool disposed between one of said end portions of said tubular member and one of said headers, electrical energy contacting means connected to said headers for providing current through said tubular member for heat processing said articles, and evacuating means communicating with said tubular member for evacuating said articles.

'14. Apparatus for evacuating and sealing articles of manufacture comprising an elongated tubular chamber for receiving said articles, means for hermetically sealing said chamber, means for evacuating said chamber, conductive means for making electrical connection with and for supporting end portions of said chamber, and means associated with said conductive means for allowing unstressed thermal expansion of said chamber.

15. Apparatus for evacuating and sealing articles of manufacture comprising a chamber for receiving said articles, means for hermetically sealing said chamber, means for evacuating said chamber, headers for receiving portions of said chamber, and means for resiliently mount- 9 ing electrically connecting said chamber between said headers.

16. Apparatus for evacuating and sealing articles of manufacture comprising an elongated tubular chamber for receiving said articles, means for hermetically sealing said chamber, means for evacuating said chamber, conductive headers for receiving end portions of said tubular chamber, and compressive conductive material resiliently mounting and electrically connecting said chamber between said headers.

17. Apparatus for evacuating and sealing articles of manufacture comprising an elongated tubular chamber for receiving said articles, means for hermetically sealing said chamber, means for evacuating said chamber, couductive headers for receiving end portions of said tubular chamber, and means disposed between one of said end portions and one of said headers for yieldingly supporting said tubular chamber within said one header and for making low resistance electrical contact therebetween.

18. Apparatus for evacuating and sealing articles of manufacture comprising an elongated tubular chamber for receiving said articles, means for hermetically sealing said chamber, means for evacuating said chamber, conductive headers for receiving end portions of said tubular chamber, and resilient conductive means disposed between one of said end portions and one of said headers for yieldingly supporting said tubular chamber within said one header and for making low resistance electrical contact therebetween.

19. Apparatus for evacuating and sealing articles of manufacture comprising an inner tubular member providing an elongated chamber for receiving said articles, said inner tubular member including a centrally disposed length made or" an electrically resistive material having a low thermal resistivity and end lengths made of an electrically resistive material having a thermal resistivity higher than that of said central length material, an outer tubular member surrounding and hermetically enclosing said inner tubular member, the inner surface of said outer tubular member being shiny and highly reflective of radiant heat energy, conductive headers for receiving end portions of said inner and outer tubular members, compressive conductive material disposed between one end portion of said inner tubular member and one of said conductive headers for making low resistance electrical contact between said one header and said one end portion, electrical energy means connected with said conductive headers for providing current through said inner tubular member, means for hermetically sealing said outer tubular member, and evacuating means communicating with said outer and said inner tubular members for evacuating said articles.

20. Apparatus for evacuating and sealing articles of manufacture comprising a chamber for receiving said articles, said chamber having a centrally disposed length made of an electrically resistive material having a low thermal resistivity and end lengths made of an electrically resistive material having a thermal resistivity higher than that of said central length material, headers for making electrical connections with and for supporting end portions of said chamber, electrical energy contacting means connected to said headers for providing current through the Walls of said chamber for heat processing said articles, and evacuating means communieating with said chamber for evacuating said articles.

21. Apparatus for evacuating and sealing articles of manufacture comprising an elongated tubular member providing a chamber for receiving said articles, said tubular member having a centrally disposed length made of an electrically resistive material having a low thermal resistivity and end lengths made of an electrically resistive material having a thermal resistivity higher than that of said central length material, conductive headers for receiving end portions of said tubular member, means disposed between one of said end portions and one of said headers for yieldingly supporting said tubular member and making electrical contact therewith, electrical energy contacting means connected to said headers for providing current through said tubular member for heat processing said article, and evacuating means communicating with said tubular member for evacuating said articles.

References Cited in the file of this patent UNITED STATES PATENTS 1,743,888 Hamister Jan; 14, 1930 1,852,800 Childs et a1. Apr. 5, 1932 1,914,741 Gysling June 20, 1933 2,520,532 Dalgleish et al Aug. 29, 1950 2,858,126 Gomez Oct. 28, 1958 2,969,412 Frank Jan. 24, 1961 3,057,130 Helwig Oct. 9, 1962 

20. APPARATUS FOR EVACUATING AND SEALING ARTICLES OF MANUFACTURE COMPRISING A CHAMBER FOR RECEIVING SAID ARTICLES, SAID CHAMBER HAVING A CENTRALLY DISPOSED LENGTH MADE OF AN ELECTRICALLY RESISTIVE MATERIAL HAVING A LOW THERMAL RESISTIVITY AND END LENGTHS MADE OF AN ELECTRICALLY RESISTIVE MATERIAL HAVING A THERMAL RESISTIVITY HIGHER THAN THAT OF SAID CENTRAL LENGTH MATERIAL, HEADERS FOR MAKING ELECTRICAL CONNECTIONS WITH AND FOR SUPPORTING END PORTIONS OF SAID CHAMBER, ELECTRICAL ENERGY CON- 